Knowledge of presence information for a mobile device in a network is useful to both the network and other mobile device users. Various applications can utilize this presence information, such as instant messaging applications, push to talk over cellular (PoC) applications, or other applications that are known to those skilled in the art.
Instant messaging (IM) is a service that alerts users when another individual, such as a friend or colleague, is on-line and allows users to send messages to each other in real time, without the store and forward delays inherent in an electronic mail solution. With instant messaging, each user creates a list of other users with whom he or she wishes to communicate (commonly referred to as “buddy lists”). An instant messaging server keeps track of the on-line status of each of its subscribed users (often referred to as presence information), and when someone from a user's buddy list is on-line, the service alerts that user and enables immediate contact with the other user. On-line status, or activity states, include examples such as “Available”, “Unavailable”, “Connected” and “Do not disturb”.
IM solutions are multiplying quickly and are showing up not only in wired environments used by PCs for example, but also in wireless environments used by mobile devices such as cell phones, smart phones, personal digital assistants (PDA's), pagers, phone enabled laptop computers and other mobile electronic devices. Wireless environments offer the potential for strong IM solutions because of the amount of time a user carries their mobile device with them.
Conventional instant messaging protocols encounter problems when deployed across wireless networks. It becomes difficult to maintain presence information for people who use instant messaging applications on their mobile device. The root cause of this problem is the inherently intermittent nature of the connection between a mobile device and a wireless network. While the conventional instant messaging protocols used to maintain accurate presence information do ultimately work for users of mobile devices, the accuracy of the mobile device user's presence as provided to other instant messaging users can suffer. Further, the necessity for a mobile device to send dedicated messages indicating presence information over the wireless network causes a greater amount of wireless network traffic, which causes a reduction in the battery life of the mobile device.